Something unprecedented is happening this weekend in Paris, brought about by the war between Israel and Hamas and its spill-over in Europe.
For the first time ever, a major demonstration attended by representatives of the major political parties will include the far right - but not the far left.
On Sunday afternoon thousands of people are expected to heed a call from the Speakers of the two houses of parliament to show their support for French "Republican" values and their rejection of antisemitism - this in the face of a steep rise in antisemitic actions since 7 October.
Among the first to announce their presence were Marine Le Pen, three-times presidential candidate for the National Rally (formerly the National Front), and the party's young president, Jordan Bardella.
Almost simultaneously came a rejoinder from their counterpart on the far left, Jean-Luc Mélenchon, irascible leader of France Unbowed (LFI). His party would not be attending, he tweeted, because the march was a "rendezvous for unconditional supporters of the massacre [of Gazans]".
It is hard to overestimate the symbolic significance of this switch-over.